Monitoring JUICE deployment operations with high-accuracy accelerometer data

The Jupiter Icy Moons Explorer (JUICE) mission is a cornerstone of ESA's Cosmic Vision 2015–2025 program devoted to the scientific exploration of Jupiter and its icy moons. Launched on April 14, 2023, from French Guiana, JUICE will perform multiple gravity assists, including an unprecedented lunar-Earth double gravity assist, in order to shape its trajectory to Jupiter, where it will arrive in July 2031. Thanks to a suite of 10 scientific instruments, JUICE will carry out a comprehensive investigation of the jovian system, with special focus on Ganymede. Among these experiments is the Gravity and Geophysics of Jupiter and the Galilean Moons (3GM) radio science and planetary geodesy experiment, supported by the onboard High Accuracy Accelerometer (HAA). The HAA, a three-axis spring mass accelerometer, measures the non-gravitational perturbations acting on the spacecraft, that need to be measured in order to fully exploit the highly accurate range and range rate measurements of 3GM. This paper analyzes the HAA data collected in the very early phase of the mission, to monitor the initial deployment of the spacecraft's moving appendages. The vibration modes of the magnetometer boom and solar arrays were clearly detected during the appendages' deployment, as well as the latching of the Langmuir probe hinges. The detected resonance frequencies of the first and second magnetometer boom bending modes are equal to 0.44 and 0.46 Hz, respectively. The HAA data contributed to identifying the root-cause of the anomalous Radar for Icy Moon Exploration (RIME) antenna deployment. The strong external perturbations due to the actuators' activation have been used to characterize the spacecraft tranquillization time. Despite the significant increase in the spacecraft noise floor during deployment events, the full sensitivity of the instrument was regained within 10 min. This information can be used to plan the spacecraft operations during the scientific phase of the mission.